conversion from opencv image to jpeg image in python

Question

I'm grabbing frames from a video file as following:

def capture_frame(file):
        capture = cv.CaptureFromFile("video.mp4")
        cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_POS_MSEC)
        cv.SetCaptureProperty(capture, cv.CV_CAP_PROP_POS_MSEC, 90000)
        frame = cv.QueryFrame(capture)
        return frame

The frame type is cv2.cv.iplimage. How can I convert this type of image to jpeg image without saving?

Thanks,

I think you can only convert to JPEG when you save! JPEG is compression procedure not opencv image type — Samer
– Samer, Commented Nov 4, 2015 at 16:58
as I already mentioned in your previous question, you should use imencode — Miki
– Miki, Commented Nov 4, 2015 at 17:44
I couldn't find a good example which shows how I can use it. — yusuf
– yusuf, Commented Nov 4, 2015 at 17:45

djsumdog · Accepted Answer · 2017-03-25 00:19:55Z

1

The following should give you the bytes for a jpeg representation of the image.

def capture_frame(file):
        capture = cv.CaptureFromFile(file)
        cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_POS_MSEC)
        cv.SetCaptureProperty(capture, cv.CV_CAP_PROP_POS_MSEC, 90000)
        frame = cv.QueryFrame(capture)
        return cv.EncodeImage('.jpg', frame).tostring()

capture_frame("video.mp4")

I've written out the results of EncodeImage to a file opened in binary (open('somefile','wb')) which resulted in a valid JPEG.

answered Mar 25, 2017 at 0:19

djsumdog

2,8281 gold badge35 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

PangolinPaws Over a year ago

FYI cv2 now has .imencode() instead of .EncodeImage()

djsumdog · Accepted Answer · 2022-09-15 20:47:02Z

0

Did you try just writing chunks?

with open('filename.jpeg', 'wb+') as destination:
            for chunk in image_file.chunks():
                destination.write(chunk)

Here's one worth looking at too that uses opencv natively http://answers.opencv.org/question/115/opencv-python-save-jpg-specifying-quality-gives-systemerror/. Although, not sure why you're trying to save .mp4 to .jpeg...

edited Sep 15, 2022 at 20:47

djsumdog

2,8281 gold badge35 silver badges65 bronze badges

answered Nov 4, 2015 at 17:01

AndrewSmiley

1,97322 silver badges34 bronze badges

2 Comments

yusuf Over a year ago

Andrew, you misunderstood me. I don't want to save the file. I have to grab the frame, and send it as a jpg file to another function as a parameter.

djsumdog Over a year ago

I wish you actually answered the original question, because I'm stuck on this as well. I need to convert an cv2.cv.iplimage to a jpeg/array-of-bytes. So far I can't find anything on stack overflow that actually does this.

Collectives™ on Stack Overflow

conversion from opencv image to jpeg image in python

2 Answers 2

1 Comment

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related